Method of treating liquid slurries to separate fibers from heavier particles



ialaiiaa oct. 12, 194s METHOD or 'rnEA'rmG LIQUID sLUnnIEs 'ro SEPARATE mEns Enom nEAvrEn PARTICLES John D. Lyall, Lancaster Township, Lancaster y County, Pa., assignor to Armstrong Cork Company, Lancaster, Pa., a corporation of Pennsyl- Application April so, '1943, serial No. 485,209

6 Claiiris.` i (Cl. 20S- 159) This invention relates to a method of treating liquid slurries and, more particularly, to an arrangement whereby the solids contained in a liquid slurry and which would normally settle out may be maintained in a substantially uniform state of suspension in the liquidj until such time as they are discharged into a mold for formation. The invention nds particular usefulness in the manufacture of mineral wool insulating blocks and the like where a water slurry of m'ineral wool bers, paper pulp bers, and asphalt emulsion is charged into a mold from a main source of slurry supply. One of the problems incident to the manufacture of such products is the tendency for the heavy mineral woolA fibers to settle out into the bottom of the bulk supply tank resulting in the discharge of a nonuniform slurry to the molds, the consistency gradually increasing in solids content as the supplyin the bulk tank recedes.

There is also a tendency for'the fibers to be 'matted during mixing with the binder and these should be opened up into more or less discreet fiber form before molding in order to obtain the maximum insulation eiiiciency.A Where mineral wool is used and proper precleaning has not been effected, the removal of shot, that is, the undrawn or unblown pellets of the material from lwhich the mineral wool is formed,-.should be eiected.

4These problems may not be present with certain types of slurries. With my method and apparatus, the fibers may be opened up and shot may be removed with facility and'where these are problems, they are eliminated by the practice of my invention. A

It is an object of my invention to provide for slurry accomplished b y means of my invention:

and t Figure 3 is a top plan view of the arrangement shown in Figure 1 illustrating the'positions assumed by the various parts within the bulk supply tank.

According to my invention, a of the slurry isv created or induced in the bulk supply by reducing the density of a limited prtion orportions of the v'slurry and directing this circulation at a rate sufcient to effect the desired results in a reasonable length of time. The rate must be controlled where the solids in the slurry are friable, like mineral wool fibers, for if too violent working of the fibers is eiected, there is a tendency for them to be broken, resulting in a short, undesirable fiber structure. The rate oi' movement or circulation must be fast enough,

' however. to maintain the fibers in suspension in the liquid against an inherent tendency to settle out. When shot removal is accomplished, thel rate must be so adjusted that the fibers are held in suspensionbut the more dense particles of shot fall to the bottom where they maybe conveniently removed. In other words, a gravity separation is eifected'directly in thesiurry supply tank.l

In the attached drawing, one embodiment of my invention is illustrated in connection with the treatment of a mineral wool, paper pulp, asphalt, and water slurry. In this arrangement, one or more conduits for the supply of gas,.preferably air, to the liquid. slurry are disposed in the bulk supply tank at a point preferably substantially below the normal level of the liquid in the tank.

maintaining a uniform distribution of the solids l in a slurry, particularly in a bulk slurry supply.

Another-object of my invention is the removal y .of undesirable heavy bodies from a liquid slurry,

such 'as the shot in mineral wool.

, Another object of my invention is to provide a system by which-any large clumps or nodules of fiber or other agglomeration of solids may be separated in the slurry'to insure a substantially uniform consistency throughout.

Other objects will become apparent from the description of the arrangement which follows, the' description being made with reference to the attached drawing in which Figure 1 isa sectional view of a bulk supply tank with the apparatus of .my invention lembodied therein;

Figure 2 is a diagrammatic view generally indieating the ilow of the ilbers and the liquid of the 'tive for supplying large volumes of air to the l best results are obtained when these conduits are spaced adjacent the bottom of the tank, close to the discharge opening. These conduits are effecslurry. The air tubes alone do not perform suc, cessfully, however, because th'e movement is gen erally lateral and no definite path or area ofcirculation is created. According to my invention, each air conduit is surrounded by a. coniiner which is effective for confining and directing the movement of the slurry which is reduced in density by the air introduced into the slurry in the vicinity of the conner. Thus, there is established or induced a definite iiow or circulation within the bulk supply; the mass or column of lower density tending to rise and the heavier and denserportions of the slurry moving downwardly to replace the upwardly moving mass. The den- 'sity of the slurry is reduced only within limited areas generally defined by the confiners. As a result, a very marked movement of the slurry is flow or circulation I l into a cleanout tube controlled by a valve- 6.

An inlet conduit C supplies slurry to the tank 2.

This may be arranged to continuously furnish slurry to the tank or it may be operated on a batch system. Disposed within the tank 2 are air inlet conduits 1 and 8, each of which is provided with a control valve and is connected to a suitable source of air supply S. These conduits extend to a point adjacent the discharge opening 9 from which the suspension of slurry is delivered to the molds for formation.

In a tank about feet in diameter and about 18 feet high, 'I have found that four air inlet'conduits 1% inch in diameter supplying air at about 10 pounds pressure are effective for obtaining a very satisfactory suspension of mineral wool, paper pulp, and asphalt in water having about a 3% to 6% solids content. Surrounding the lower end of each of the air inlet tubes 1 and l are conners I0 and I I which are circular in cross section in the embodiment shown, about l2 inches in diameter, and about 3 feet long. The coniiners are mounted upon supports I2 which are embedded in the concrete of the conical lower portion 4 of the tank 2. 'I'he size and shape of the conilners are not critical but they should be proportioned to take into account the type of material being operated upon, the size of the tank, and the quantity of solids in the slurry being operated upon. With certain types of slurres, a single air conduit and confiner may be provided in the center of the tank and this will be effective for obtaining the desired results. The length of the conflners determines to some degree the extent of the circulation along the vertical axis of the tank. When conners of small diameter are used, circulation of higher velocity may be obtained with the same volume of air for the circulation is dependent upon a reduction of density in the mass of slurry and a greater density reduction is accomplished in a smaller volume of slurry With the same volume of air. I have found that particularly good results are obtained if the conduits supplying air extend a slight distance below the confiners. A distance of about 2 inches has been determined to give particularly satisfactory results on initiating a circulation within the slurry.

Figure 2 indicates generally the action which occurs within the bulk'supply tank when the air is fed through the air conduit 1. The air is under pressure and |i'lrst moves downwardly and then upwardly through the conflner Ill. Since the slurry within the conner I0 includes not only the solids and the liquid but also the air, the density oi.' the column within the conner and thereabove is reduced and moves upwardly. As this portion moves upwardly, additional slurry is drawn into the conflner as indicated generally by the arrows in Figure 2. This induces a ow of considerable magnitude within the tank. With four coniiners as shown in Figure 3, there will be four distinct areas of motion or circulation within the tank due to the decrease in the density of the column of slurry generally dened by the diameter of each coniiner. The admission of airis controlled by the valves in the conduits l and I so as to maintain the fibers in` suspension but insumcient air is admitted to eilect a rate of circulation sufficient to carry the more dense and heavier shot particles. There is a change in velocity from the downward vertical path of circulation to the horizontal path entering into the conflners and this is adjusted so that the shot which are heavier than the bervmerely continue downwardly while the bers move horizontally into the conilners. The shot settles into the bottom of the tank below the discharge opening 9. There is some turbu-` lence within the conners and thereabove and this effects a general opening up of any clumps or agglomerations of fibers or other solids which may be present. As the operation continues, the entire mass of slurry is acted upon and a uniform sus pension is obtained which may be maintained in that condition indefinitely by vcontinuing the circulation of the slurry. The system is preferably operated on a continuous basis and a fresh supply is furnished through inlet C to replace material discharged through the opening 8 to the molds for formation. At the end of a day's operation, or more frequently if necessary. the inlet C may be closed and after the tank is emptied through the discharge opening 9, the valve 6 may be opened and the shot removed,

By this invention a uniform product may obtained regardless of the particular level of liquid in the bulk supply tank. A substantially uniform dispersion of the solids is eilected and maintained, any clumps of entangled fibers may be separated, and heavy shot or other undesirable foreign bodies may be removed.

While I have illustrated and described a preferred embodiment of my invention, it will be understood that the same may be otherwise embodied and practiced within the scope of the following claims.

I claim:

1. In a method of treating a liquid slurry containing flbers and undesirable heavier particles, a substantial portionof the solids of the slurry having a tendency to settle out, the steps of establishing al circulatory movement within the body of slurry in a generally upwardly and downwardly direction by injecting a stream of air downwardly into the slurry, confining the upwardly moving portion of the slurry separate from the downwardly moving portion in a zone spaced from and above the point of air injection and accelerating the upwardly moving portion of the slurry with respect to the downwardly moving portion in said zone, and adjusting the differential in rate between the upwardly and downwardly moving por tions to draw the bers out of their downward' ltravel into the upwardly moving portion but insuiiicient to draw the undesirable heavy particles out of the downwardly moving portion.

2. In a method of treating a liquid slurry of mineral wool ilbers containing undesirable heavier particles, a substantial portion of the solids of the slurry having a specific gravity greater than the liquid and tending to settle out, thesteps of establishing a circulatory movement within the body of slurry in a generally upwardly and downwardly direction by injecting a stream of air downwardly into the slurry, with the upwardly moving slurry confined and separated from the downwardly moving portion in a zone spaced from and above the point of air injection, movement of said slurry being accelerated with respect to the downwardly moving slurry throughout at least a portion of its travel in said fai 3. In a method of treating a liquid slurry coni taining fibers and undesirable heavier particles,

-a substantial portion of the solids of the slurry having a tendency to settleout, the steps of establishing a circulatory movement within the l body of slurry in a generally upwardly and downwardly direction by injecting a stream or air downwardly into the slurry, confining the up.. wardly moving portion of the slurry separate from the downwardly moving portion in a zone spaced from and above the point of air injection and accelerating the upwardly moving portion of the slurry with respect to the downwardly moving portion in said zone, effecting a turbulent motionl within the confined portion, and adjusting the movement of the slurry to draw the desired fibers out of their downward travel and into the upwardly moving portion of the slurry where the iibers are separated by the turbulent movement, the accelerated movement of the upwardly directed portion of the slurry being insuiiicient toA draw the undesirable heavier particles out of the downwardly moving portion 'whereby the heavier particles are settled out and the desirable iibers are maintained in suspension within the slurry.

4. In a method of treating a liquid slurry of mineral wool fibers containing undesirable heavy particles of shot or the like, the steps of establishing a circulatory movement within the body'of slurry in a generallyupwardly and downwardly direction by injecting air downwardly into the slurry and confining the upward movement of the air through the slurry in a zone spaced lfrom and above the point of air injection and separated from the downwardly moving portion of the slurry to thereby accelerate the upwardly moving portion thereof with respect to the downwardly moving portion in said separated zone, and adjusting the rate of upward movement to a velocity sumcient to draw the fibers of the slurry from their travel in a downward direction into the ,ac-

celerated upwardly moving stream-but insuiiiv -cient' to draw the undesirable shot particles or the like into the upwardly moving stream whereby the shot particles or the like are settled out.

5. In a method of treating a liquid slurry containing fibers and undesirable heavier particles, a. substantial portion of the solids of the slurry having a tendency to settle out, the steps of establishing a circulatory movement within the body of slurry in a generally upwardly and downwardly direction by injecting a stream of air downwardly into the slurry, confining the `upto reduce the density ofthe slurry in a limited portion only oi the body thereof to a degree where the desired iibers will be suspended in the liquid and thereby accelerating the upwardly moving portion of the slurry with respect to the downwardly moving portion in said zone, and ad- -justingthe differential in rate between the upwardly and downwardly moving portions by altering tlie density of the slurry in said limited portion to a velocity where the iibers will be drawn out of their downward travel into ,the upwardly moving portion but the undesirable heavy particles will not be so drawn out, the density of the slurry in the limited portion of the body being adjusted to a point where desired iibers will be suspended and the undesirable particles will settle out.

6. In a method ofl treating a liquid slurry containing bers and undesirable heavier particles,

a substantial portion of the solids of the slurry having a tendency to settle out, the steps of establishing a circulatory movement within the body of slurry ina generally upwardly and downwardly direction by injecting a stream of air downwardly into the slurry, confining the upwardly moving portion of the slurry, separate from the downwardly moving portion in a zone spaced fromv .and above the point of air injection and accelerating the upwardly moving portion of the slurry with respect to the downwardly moving portion in said zone, adjusting the differential in rate between the upwardly and downwardly moving portions to draw the fibers out of wardly moving portion of the slurry separate from the downwardly moving portion in a zone spaced from and above the point of air injection REFERENCES crran The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name A Date 664,712. Baldenebro Dec. 25, 1900 751,645 Hopkins Feb. 9, 1904 830,552 Zeigler Sept. 11, 1906 1,180,089 Thompson et al. 'Api'. 18, 1916 1,253,653 Welsch Jan. 15, 1918 1,405,126 Harris Jan. 31, 41922 4 2,105,101 Stelley Jan. 11,v 1938 2,174,540 Wallace Oct. 3, 1939 2,243,302' Weinig May 27, 1941 2,284,459 'Watkins May 26, 1942 2,386,713 Pharo Oct. 9, 1945" FOREIGN PATENTS Number Country Date 9.038 Great Britain Apr. 20, 1904 167,504 Great Britainl July 27, 1922 352,931 Great Britain July 10, 1931 

